Storm choke



July 24, 1962 H. H. MOORE, JR 3,045,760

STORM CHOKE Filed Nov. 1?, 1958 H. H. Moore, dr.

INVENTOR.

ATTORNEY $345,754] Patented July 24, l962 3,045,760 STORM CHOKE Howard H. Moore, Jr., Houston, Tex., assignor to Cameo, Incorporated, Houston, Tex., a corporation of Texas Filed Nov. 17, 1958, Ser. No. 774,300 1 Claim. (Cl. 166-224) This invention relates to well tools and more particularly to an improved storm choke for installation in a production or flow conduit of a well and for automatic operation to close the conduit in response to abnormal flow conditions in the nature of an unrestricted outrush of pressure fluid as might occur due to failure or breakage in a region of the conduit upstream of the automatic closure. Damage to surface equipment may come at any location and from various causes including careless handling. it is most bothersome at offshore wells, whose equipment during storms is often subjected to violent bulfeting forces.

An object of the invention is to provide an improved safety cutoff or blowoff preventer having a pressure fluid closure operable to minimize the likelihood of fire and the loss of valuable gas and oil fluids, as well as costly remedial procedures, should the surface equipment at a well become damaged or broken.

A further object of the invention is to provide a safety unit having its parts arranged to afford a straigh"-through or linear flow passage which avoids stream turns and impact surfaces productive of eddy disturbances and accelerated friction wear from sand and other abrasive entrainments in the pressure fluid.

Another object of the invention is to provide a simple and low cost assembly comprising a readily applied retrievable mounting tube to fit within and in sealed relation to a flow conduit and to house a slidable tube having a straight-through constricted passage in axial alignment with the conduit and providing a choke of predetermined dimension whereby fluid pressure differential on opposite sides of the slider tube tends to carry and shift the tube upstream and does so at a predetermined differential value set beforehand by a selected opposing spring force and which travel of the tube removes an end portion thereof from the inward swing path of a hinged flap valve and permits the valve under the action of pressure fluid to swing inwardly and upwardly into seating relation with the tube end for thereafter maintaining the conduit closed against further outflow.

Additional objects and advantages will become apparent from consideration of the accompanying drawing wherein FIG. 1 is a vertical sectional view of the tubing string portion in which the improved flow control valve is located and FIG. 2 is a vertical section of the lower portion of the control device illustrating the parts in conduit closing relation.

Referring to the drawing, there is shown a portion of a production conduit or tubing string for connecting surface equipment with a well production formation and the string includes the usual tubing section 1 in which there is coupled at a given depth location a conventional nipple 2 of the type generally used for fitting and hanging flow control units of various kinds. The lower portion of the usual hanger 3 carries a number of peripheral sealing rings 4 for closing fitment to the interior of the hanger receiving nipple 2 for sealing against fluid flow. At its lower end the hanger 3 has screw threaded coupling connection for attachment with a flow control device which in the present instance and as will be fully described, includes an outer mounting member or tubular housing, an inner tubular choke member slidable within the housing in the direction of fluid flow there through, and a swingable flap valve pivotally mounted at the bottom of the outer housing for co-operation with the lower end of the slide tube.

The tubular housing includes an end to end succession of sections 5, 6 and 7 having their adjoining ends screw threaded one upon another and the sectional assembly facilitates manufacture and assembly. The upper end of the upper section 5 has screw threaded con nection with the tool hanger 3 and at its lower end is externally threaded for connection to the upper end of the intermediate section 6. For a short distance above its lower screw threads, the upper tube section 5 is of reduced diameter for receiving an annular sleeve 8 which co-operates with a counterbored radially extending port 9 through the wall of the housing section 5. Within the counterbored port 9 is an outwardly opening valve 10 which normally is spring seated inwardly of the conduit passage. The valve 10 includes a short stem which extends inwardly into the passage to be engaged by a wire line actuated plunger rod for unseating the valve 10 and thereby communicating the interior of the tool passageway with the surrounding tubing space. When the valve 16 is unseated, the communication is by way of its bore 9 and a small aligned port' in the sleeve 8.

Immediately below the interiorly screw threaded upper portion of the intermediate housing section 6 is an internal counterbored portion of successively stepped diameters providing an interior chamber comprised of an upper large diameter portion 11, a next adjoining smaller diameter portion 12 and a lower adjoining additionally smaller chamber section 13. These chambers are to be filled with a suitable liquid such as a silicon fluid, which can be introduced through a lateral port 24 in the housing section 6, shown in the drawing as being closed and sealed by a tubular sleeve 23, closely fitted on an annular recess in the housing section 6 just above the upper end of the housing section 7. This liquid filling co-operates with a piston afiorded by an annular peripheral rib 14 on the slidable tube 15. In the normal position of the parts, the under surface of the rib 14 has seating engagement with a mating upwardly facing shoulder afforded internally of the housing section 6 between the stepped diameter chambers 12 and 13. The shoulder thus constitutes a stop limit for slide travel of the tube 15 in a downward direction. A stop limit to travel in the upward direction is afforded by the bottom terminal face of the housing section 5 upon engagement therewith by the upper face of the tube carried rib 14. Peripherally the rib 14 fits the internal cylindrical face of the chamber 12 with a predetermined clearance for affording a small flow space or passage around the movable rib or piston 14 whereby to retard the rate of travel and afford a dashpot action which also minimizes the likelihood of slide tube vibration when opposing forces thereon are close to equality. The longitudinal length of the rib 14 is somewhat less than the length of the larger chamber portion 11 and is less than the length of the intermediate chamber section 12 to which it is closely fitted. Accordingly, upward movement of the tubular inner member 15 through the initial part and for more than half of its range will be closely controlled by the displacement of liquid from one side to the other but in the final range of travel the close clearance fit of the parts is eliminated after the rib passes out of the chamber 12 and into the larger chamber 11 for permitting an accelerated rate of travel at the end of the stroke.

Above and below the dashpot chamber, the slide tube 15 has guided bearing engagement with the housing sections 5 and 6 and the slide bearing surfaces preferably are sealed or packed by means of O-rings, shown at 16.

At its lower end the slide tube 15 has detachably threaded thereon an enlarged head 17 of a replaceable tubular valve seat 18 which forms a lower tubing extension or continuation of the slide tube 15. interposed between the head 17 and the bottom of the housing section 7 is a coiled compression spring 19 whose elastic force yieldingly biases the slide tube downwardly toward its lower limit. The coiled spring 19 is protectively enclosed within a dead-ended pocket between the lower housing section 7 and the slide tube 15. The size and strength of the spring 19 will be selected to overcome within a given range the differentials in pressures below and above the slide tube 15 and which act against the opposite upper and lower ends of the tube. The internal diameter of the slide tube 15 is correlated to flow diameters on opposite sides of the slide tube so as to introduce a restriction in the flow path. When the path is fully open, as seen in FIG. 1, it extends in a straight line entirely through the tool as a parallel or coaxial continuation of the conduit passage through the tubing string. Because free flow is choked, there will occur a drop in pressure across the slide tube during pressure fluid flow toward the surface and the higher pressure acting on the lower end of the tube will tend to carry the tube against the elastic restraint of the coil spring 19. I

When the surface equipment at the well is valved into the usual gathering lines, resistance to fluid flow upstream of the tool will prevent a Wide pressure differential on opposite sides of the slide tube 15. However, should flow resistance be decreased, as may occur upon a break in the flow conductor and control equipment at the surface, the loss of back pressure upstream of the choked tool will widen fluid pressure differential across the slide tube. When the unbalance is sufficiently great to overcome the elastic opposing force of the coil spring 19, the slide tube 15 will rise upwardly until the dashpot piston 14 reaches the end of its travel and is stopped by abutment with the lower terminal face of the housing section 5.

Advantage of the positions assumed by the slide tube 15 under different well conditions is taken for controlling the fluid flow, or more properly speaking, for controlling the closing action of a co-operating pressure responsive valve. As here shown, the bottom annular edge of the tubing extension 18 is tapered and affords a seat for cooperation with a flap valve 20 mounted at the lower end of the housing section 7.

The valve 20 is constituted by a flat disk having side extensions or forked arms to receive therebetween the bottom end of a C-strap 21 carrying a hinge pin 22 to project through the side arms of the valve for swingably mounting the flap valve 20 on a transverse horizontal axis laterally of the slide path of the flow restriction tube 15,

ing 7 and the vertical bar of the C-shaped member is of a transverse dimension substantially corresponding with the radial clearance between the tubular sections 7 and 18, whereby the valve mounting member 21 is held against displacement. Both the mounting member 21 and its valve 20, as well as the tubular end seat 18, can be readily removed and replaced upon separation of the lower housing section 7 from the intermediate housing section 6 and without disturbing or otherwise disassembling the rest of the flow control unit.

In normal well operation, the relation of the parts will be as shown in FIG. 1, wherein the dependent flap valve 20 hangs downwardly from its pivot mounting and beside the downwardly projected slide tube 15. In this position the flow passage through the conduit is open and the slide tube provides a straight-through path in linear alignment with the flow conduit. Lateral engagement between the downwardly projected tube extension 18 and the flap valve 20 will pocket the valve against inward swinging movement.

Should this lateral obstruction be removed'by tube upward retraction upon pressure differential overcoming the force of the spring 19, the outrush upwardly of pressure fluid along the inward face of the swinging valve will tend to rock it inwardly and upwardly and toward seating engagement with the lower end or seating tip of the elevated extension 18, as seen in FIG. 2, whereupon pressure below the valve will maintain it in seated tube closing position, for cutting off further upflow of well fluid.

The relationship of the parts is such that the rise of the slide tube 18 to the valve closure position will be established by the seating abutment of the piston rib 14 with the bottom end face of the housing section 5. A tight valve seating fit can be had without extreme manufacturing accuracy when the lateral legs of the C-shape mounting member 21 fit within their retaining openings with a limited degree of looseness sufficient to permit a slight longitudinal movement of the C member 21 relative to the housing section 7.

Once the flap valve has closed the passage against pressure fluid flow, it will remain sealed against loss of pressure through a broken surface connection and enable necessary repairs to be made. When that has been done and it is again desired to flow the well, a suspended weighted rod is lowered from the surface to reopen the flap valve. Such rod can be one which will fit through the upper end of the tool hanger and depress the valve 10 by engagement with its inwardly extended stem, for approximate equalization of pressures above and below the slide tube, whereupon the latter will be projected by its spring 19 for again opening the valve 20. Optionally, an equalizing prong can bear directly on the upper surface of the slide tube 15 and exert downward force to supplement the spring 19 in pushing the tube 15 downwardly for opening the valve and re-establish the condition in which the spring force again exceeds fluid pressure differential.

What is claimed is:

In a well tool, an outer housing tube, an inner tube longitudinally slidably mounted in said housing tube and provided with a restricted pressure flow passage, spaced apart stop abutments on said tubes establishing upper and lower limits on slide tube travel, a normally open flap valve co-operating with the lower end of said slide tube, means pivotally mounting the flap valve on an axis above the lower end of the tube at its lower slide travel limit and in lateral engagement with the tube side wall above said lower end when the tube is at its lower limit and for inward and upward swing travel into valve seating closure engagement with said tube end when the tube is at its upper limit and means comprising a lost motion connection joining the pivot mounting means and said outer tube and accommodating their relative shift movement in the direction of longitudinal slide tube travel.

References Cited in the file of this patent UNITED STATES PATENTS 1,022,171 Ballard Apr. 2, 1912 2,403,186 Leslie July 2, 1946 2,690,226 Comstock Sept. 28, 1954 2,812,821 Nelson Nov. 12, 1957 2,841,171 Baker et a1. July 1, 1958 2,857,003 Boyd Oct. 21, 1958 2,896,917 McGarrahan July 28, 1959 2,921,601 Fisher -1 Jan. 19, 1960 2,931,384 Clark Apr. 5, 1960 2,981,336 Ansite Apr. 25, 1961 2,984,303 Baker May 16, 1961 

